94 Ranger TC lock-up problem

[Professor2]

I have a 94 Ranger V6 with a A4LD. I have a TC lock-up problem. I rebuilt the trans a little over a year ago. It kept getting slower to go into gear so I took it to a trans shop and they rebuilt the trans and put in a new torque converter. It shifted nice but only went into TC lock-up a couple of times.I have taken it back to the trans shop 6 times. They first changed the govener and a solenoid. That didn't fix it. The second time they changed the valve body, no good. The third time they changed the torque converter, still no good. They changed the solenoid again and still no good. I changed the PCM with the exact same part # and it does exactly the same thing.
I can reset the codes and it will shift perfect for about 8 times then it quits. I have tried to read the codes but I don't get anything useful.
My question is: is there anything besides the solenoid for TC lock-up, torque converter or valve body that will cause no lock-up? Maybe something on the engine like TPS or MAF or ???
I'm really tired of disconnecting the battery everytime I drive to reset the codes or whatever it is resetting.
Any help is greatly appreciated!

 

[F150hybred]

Just a wild thought, but check the ground strap from the firewall to the engine/bell housing. Could be as simple as a bad ground (not hooked up by the transmission shop).

 

[Professor2]

I looked for the ground from the firewall to the trans but couldn't see one. Where is it? i was under the trans and couldn't see it. The battery ground is on the starter bolt which goes to the bell housing but that doesn't gnd the body which is where the PCM is.

 

[F150hybred]

It should be a woven cable going from the firewall to the top bell housing bolt.

 

[Professor2]

I can't see the back of the engine from the top and I can't get my hand up there from the bottom. I think I'll just make another ground for it. It won't hurt if it has two and it will help if it has none. Thanks for the Idea to look for a ground. I will post again if does or doesn't fix it.

 

[Professor2]

I was looking for a good place to put a ground wire and I found the factory gnd. It was attached to the firewall by the windshield motor and to the back of the head. I loosened both ends and moved them around and retightened them. I haven't driven it yet so I don't know if it fixed anything.

The problem must be somewhere other than in the trans because it shifts correctly for 8 or 10 times then it stops working.

 

[Professor2]

I just did a test drive and it is still the same. What can I do now to make this thing work?

 

[F150hybred]

Sorry, I'm at a loss for now. I'll keep it in my head though and if I come up with anything, I'll post it.